Undetectable
by LemurLou
Summary: This is a medical fic in which Cameron becomes ill and the team, of course, has to diagnose her in time. No ships.


**Chapter 1**

Cameron gasped for air as she lifted up her head and wiped off her mouth. By far, this was the worst day she'd even experienced. She'd spent all of last night either sitting on the toilet or hunched over it. Cameron had hoped it was just a twenty-four hour bug, but if anything it was just worse this morning…

She slid over and rested her face against the cool tile of her bathroom wall. Cameron tried to take a drink of her Gatorade, which she'd prescribed for herself, but ended up gagging so much she closed her eyes and gave up.

The phone rang, but she couldn't muster the strength to go answer it. Cameron just let it ring through.

"It's House. We have a patient in the ICU. Where the hell are you? If you're not at work in a half hour, I'm coming to your apartment." Cameron sighed, then suddenly leaned her head over the toilet and retched. Just moving from the wall of her bathroom over to the toilet took it all out of her. No way was she going in to work. She just prayed that House would follow up on breaking in. Because otherwise, she was just going to rot.

When she threw up again, she realized she was vomiting blood. And that was when she became sure that House was going to be her savior. If she wasn't so sick, she might have enjoyed it.

**Chapter 2**

"Sht," House swore under his breath. He cursed himself for not coming earlier. She was crumpled in the corner, pale, eyes closed. She seemed to be sleeping, but she kept moaning and thrashing. There was a mostly untouched bottle of Gatorade rolling around on the floor, a horrible smell, and a mixture of blood and vomit staining Cameron's mouth, chin, and clothing.

"Cameron?" Her eyes flew open, and she screamed. Shaken, House limped quickly out to her kitchen and picked up the phone.

"What is the nature of your problem?" The operator asked.

"I'm at four Hawthorne Road, Princeton. I need an ambulance."

"I'll dispatch one now, sir." House hung up and went back to Cameron. He flushed the toilet, then carefully sat himself down next to her.

"How long have you been sick?" He asked. She made a guttural animal noise.

"Last… last night," she rasped. House nodded. Cameron screamed again. He felt the bottle of Vicodin in his pocket.

"Here." He opened the bottle and held one out to her, along with the Gatorade. After three tries, she swallowed the pill and fell asleep in his lap.

**Chapter 3**

When the ambulance showed up, House told the paramedics over and over not to wake her. Then he told them to take her to Princeton-Plainsboro. The bald man who he'd pestered about letting Cameron stay asleep was pissed, but bowed to House's request. A pretty young woman who looked dead-tired sat in the back and performed the basic tests. Then, she turned to House.

"I'm going to need you to give me some information. What's her name?"

"Allison Cameron."

"You're her… husband?"

"Employer. She was late to work, I broke int…"

"I didn't hear that. You _used your key_, and then…" House grinned.

"I found her in the bathroom like this."

"She was drugged?" The paramedic looked up from her paper, and she looked him right in the eyes. House sighed.

"I have a prescription for Vicodin and I gave one to her."

"Please tell me that you're a doctor." House nodded.

"Well, that's a step." The woman rolled her eyes, and leaned in. "We had this one woman who died. She had this disastrous intestinal infection, vomiting every ten minutes, completely dehydrated, and the husband gives her… wait for it… Ipecac." House snorted, but before he could open his mouth again, the bald man was barking at everyone to get out of the way so he could wheel Cameron off the ambulance.

**Chapter 4**

Cameron tried desperately to bring he eyes into focus. She was feeling better, her stomach cramping reduced to a dull ache and her nausea staying low. She guessed she was heavily drugged.

"H…ouse…?"

"Nope. It's the whole crew." Finally, Cameron brought her eyes into focus and saw House, along with Chase and Foreman. Suddenly, the nausea sprung up again and she quickly located her emesis basin.

"I generally prefer 'hello,' but I suppose that'll do." House said as he limped over to read her monitors. Chase rolled his eyes at House, and Cameron smiled vaguely.

"What do you have me on?" She asked.

"Cocaine." House answered.

"No, seriously." Cameron was not willing to sift through his jokes for a straightforward answer. Foreman spoke up.

"Varying doses of morphine, intravenous Emetrol, and a milligram every six hours of Ativan. How's it working?" Cameron shut her eyes and leaned back into the pillow.

"Wonderfully. Can you up the morphine?" Chase took out his key and a few beeps later, marginal relief flooded Cameron's system. With inane well-wishes, the healthy members of the Diagnostics team left. The visit with Cameron had told them only one thing: they needed to a diagnosis even sooner than they'd thought.

**Chapter 5**

"Say it with me." House motioned with his arms. "It's time for…"

"Differential Diagnosis," Foreman and Chase finished, out-of-sync in boredom. House uncapped a marker with his teeth.

"Okay. So far, all we got is vomiting and stomach pain. What do you think?" Foreman sighed.

"That could signify thousands of illnesses."

"Pick one." Foreman rolled his eyes.

"Uh… food poisoning." House squinted.

"That would have to be the turkey sandwich from hell. Try more severe."

"Intestinal blockage."

"Who wants to test for that?"

"I'll…" Chase began, starting to stand up.

"We know you've always wanted to shove _something _up Cameron's ass. Up 'til now, I didn't know it was a Barium enema. Right shape, though. Next time, think less… plastic." Chase rolled his eyes and left. House turned to Foreman.

"Any other ideas?"

"Septic shock?"

"Plausible. Get blood tests. If she starts having seizures, you're probably right." Their pagers went off.

"Chase," Foreman muttered. His voice went up in panic. "He needs us in there now." They took off down the hallway, hoping they could get there in time to help Chase, and, more importantly, save Cameron.

**Chapter 6**

Five minutes later, Cameron was unconscious and the nurses were cleaning her up.

"You seen the Exorcist?" House asked, as he, Chase and Foreman sat on the bench outside Cameron's hospital room. The Exorcist analogy was more or less on target. Cameron'd had one of the most severe grand mal seizures any of them had ever seen. Spewing vomit, completely incontinent, limbs flailing in every direction and her back arching so far they were afraid it would damage her spine. Only a Valium level bordering on heart-stopping had ended it. When she was stable, they'd all resumed their positions outside her hospital room, panting from the effort of holding her down. After several moments of silence, Foreman turned to House.

"Sepsis?" House nodded.

"Get the blood tests, but I can't imagine it isn't. Wonder where she got it, though." House was unsure of his words before they left his mouth, but didn't take them back. Foreman, not noticing House's uncertainty, shrugged, got up and came back five minutes later with two crimson vials.

"Wish me luck," he said, walking down the hallway and disappearing into the lab.

"I do," House muttered. He got up and left for his office. Chase remained on the bench. And in the part of his mind that wasn't taken up by worry, he realized he never had gotten to do that Barium enema.

All three of them waited with there stomachs in knots. (Cameron's waited in violent revolt.)

But one way or another, everything hung on the results of Foreman's cultures.

**Chapter 7**

"Negative," Foreman came back and dropped Cameron's file on the table. House and Chase let out their long abated breaths. This was bad and good news: she didn't have to undergo the dangerous treatment for sepsis, but they still had no idea what was wrong. Slowly, House got up and erased "Sepsis?" from the whiteboard. On the left column, his shaky scrawl had inked "Nausea/Vomiting, Seizure". He drew a line down the middle and headed the right column with "DDX". Foreman and Chase passed the folder back and forth. House hummed the Jeopardy theme song.

"I know this is a long shot, but what about brain cancer?" Chase mused. Reluctantly, House wrote it down.

"Anything with a more promising prognosis? Come on. Don't kill the girl with your hypotheticals." When they said nothing, he continued. "These are two of the most generalized symptoms out there. Don't tell me you can't come up with anything useful." Chase threw down the folder.

"You want me to rattle off a list? Okay. A concussion. No trauma. Fructose allergy. Blood sugar levels are normal. Severe kidney disease. Urine output is average and isn't a funny color. Drug abuse. No way. Come on, we know Cameron." When Foreman suppressed a snort, Chase added angrily, "Okay. _One _time she stole someone's meds. That doesn't mean she's getting this from a barbiturate OD or pot. The problem is that she's _healthy. _She's a young, healthy, rich female WASP. She's in _no _risk groups."

"Other than, say, working around sick people all day." House snapped back. Foreman looked up from the file.

"Naelgleria." He suggested. House spun around.

"I'm sure you're familiar with it. Spinal tap for the _n word_," pointed look at Foreman, "meningitis, and any other menigoccocal disease you can think of. Chase, do an MRI. Check for hemorrhage, injury, or…" he paused, "a tumor. The infection theory's less likely, because she doesn't have a meaningful fever, but it's still possible." Chase and Foreman got up to complete their assigned tests, both with the sinking feeling that instead of swimming forward, they were simply treading water. And one way or another, soon they would be forced to simply get out of the pool.

**Chapter 8**

"You know the drill," Chase said, carefully curving Cameron inwards and preparing the needle. She whimpered a little.

"Do you have any idea what's wrong with me?" She asked, her voice hoarse from the digestive acids that'd been torturing it all day.

"We have some… theories."

"You have no idea. We talk to patients like that when they're dying and we don't have a clue." Chase passed the needle between her vertebrae easily and held a vial to catch the clear CSF.

"You don't have menegitis," Chase offered pitifully. "Your fluid's clear." Cameron didn't respond.

"Cameron?" He asked, quickly sealing the vial and taking the needle out of her back. The monitors began to go wild.

**Chapter 9**

House sat splayed out on his floor with his four notebooks and piles of old medical books and journals. He re-read the notebook page that his most recent one was open to. House kept a record of the symptoms and diagnosis of every patient he'd ever had in a plain marble notebook. Cameron was no exception.

Nausea and Vomiting – antiemetics min. help

Stomach Pain- morphine drip

Grand Mal Seizure (1) – Ativan, Depakene, IV Phenobarb

DDX: Sepsis? Menig.?Nagleria (like Fore.)? Tumor/Injury/Hemorrhage?

They'd all been crossed out, because none fit the next symptom. House's handwriting, seeming small and nervous, had penned:

Cardiac Arryth. – 3 dose epi

He'd gone through textbook after textbook, he'd gone through his notebooks of other patients . Looseleaf papers tortured by angry lettering were scattered around him. And he couldn't focus because of all the noise Steve was making on his wheel in the kitchen.

"I swear, if you don't stop that damn _spinning_, I'm going to kill yo…" He paused.

House had his diagnosis.

**Chapter 10**

"What the…" The phone started ringing second's after House's epiphany.

"House? It's Chase."

"Who else do we know who likes to annoy me and talks funny?" Chase sighed.

"Cut it out."

"Why are you calling?"

"Cameron's losing her hair."

"Doesn't surprise me." Chase faltered, then realized what House meant.

"How long have you known what's wrong with her?"

"Seconds. I'm coming over to PPTH." House hung up, shoved his patient notebooks in his messenger bag, grabbed his car keys, and moved as fast as he could out the door.

"Thanks, Stevo!" He yelled to his rat on the way out. Off to PPTH. Off to save the day.

**Chapter 11**

"Hook her up to a potassium ferrihexacyanoferrate IV, flush her system with activated charcoal, and I want her on potassium chloride and a low-dose diuretic." Foreman and Chase stood there, looking exhausted and confused.

"_What_?" House sighed and started down the hall to Cameron's room. He stopped dead in his tracks. She was worse, way worse than she'd been just a few hours ago. The preposterously small emesis basin had been replaced by a small, hospital-green trash can that was nearly a quarter full. Chunks of Cameron's beautiful brown hair lay on the floor, but the strands under her head were dampened by the mixture of saliva and vomit that trickled continuously from the corner of her slack mouth. Cameron herself was unmoving and unresponsive. Her heart and pulse monitor lay constantly in the realm bordering unacceptable. The room smelled of an unflushed public toilet.

Suddenly, House yelled.

"Get the dmn treatment!" Unfrozen, Chase ran out of the room to the pharmacy and Foreman began the superfluous sedation for the charcoal flush. Once the tube of black slurry was flowing, Foreman turned to House.

"What's wrong with her?"

"She has thallium poisoning." Foreman made an expression that indicated a desire for further explanation.

"Blue-black metal. TI on the periodic table." Foreman rolled his eyes.

"I know what it is. How did she _get _it?" House shrugged.

"When she's sentient again, we're all going to her apartment and…" Chase came in with three IV bags, and he got busy setting them up.

"So what _is _wrong with her?" House told him, and once the medicine was dripping into Cameron's bloodstream, the three men settled in to throwing possible sources around for hours. But really, they wouldn't know until Cameron was better.

**Epilogue**

"You fcking moron!" House yelled from Cameron's kitchen. "You have _got_ to be kidding me!" He sounded somewhere between amused and horrified. Cameron, Foreman and Chase came running in. They hadn't gotten used to Cameron with a pixie cut yet, but it was cute on her.

"What?" House held up a small block of cheese covered in a torn-open red wrapper.

"You have a mouse problem, don't you?" Cameron nodded.

"You _ate _the mouse poison. Thallium is used in cheese to poison rodents. You had it in your fridge. I'll bet were eating over the sink, bad lighting and didn't notice…" Cameron stood there, pale, mouth hanging slightly open. Foreman and Chase stared at her. House slammed the cheese down on the counter.

"Congratulations, Cameron," he said. "You are the second patient of mine to die from cheese."

The men packed up their stuff to leave. And Cameron stood in front of the block of cheese, staring, unable to believe what she'd done.

**Author's Note**

Thallium is not generally a source of poisoning in humans. It's an element, a blue-black, soft metal that has no (known) biological purpose. It's found in small amounts in cigarettes and is used in the camera-making industry. Sometimes, like in this story, it's used as rat poison.

Thallium salts are completely tasteless, odorless, and colorless. They dissolve completely in even small amounts of liquid. Hence the title of this fic. Thallium salts are often completely undetectable. (And in the story, although they found the poisoned cheese, Cameron had not noticed what she was consuming that night she'd been "eating over the sink.")

On the rare occasions thallium _is _used for murder, it is extremely effective and difficult to trace. During WWII, the Americans poisoned the Nazis' drinking water. They all died of seemingly different causes, the only symptom in common their loss of hair. And in the movie that inspired this fic, A Young Poisoner's Handbook, the main character got away with (literally) murder for years.

But lots of things in this world are dangerous. Cancer, car crashes, house fires. Don't lie awake too many nights worrying about thallium poisoning.

It is fascinating, though, isn't it?

-Leems


End file.
